Heat exchangers are widely used to dissipate heat. One application is to protect sensitive electronic controls that are located in harsh industrial settings.
Heat exchangers having convoluted aluminum cores are preferred for providing closed loop cooling for enclosed electronics. In such a heat exchanger, heated enclosure air is drawn through one side of the convoluted core while cooler ambient air is pulled through the convolutions on the other side of the core in the opposite direction. Heat from the enclosure air transfers through the core to the ambient air flow and is discharged into the atmosphere. The cooled enclosure air then blows back into the enclosure. Such a heat exchanger is ideal for applications in which the electronic controls can operate at a temperature differential slightly above ambient, humidity is not a factor, and ambient air contaminants must be kept out of the enclosure.
Previously, convoluted cores were made by simply manually folding a sheet of aluminum. Various types of devices are known in the art for forming, crimping, folding, perforating and otherwise processing sheet or strip material, such as sheet metal. But these devices are generally not suitable for making the convoluted aluminum cores used in closed loop heat exchangers.
One device used in the automotive industry for manufacturing radiator cores is a rolling fin machine that utilizes a gear mesh operation to form the convolutions as the sheet material passes between the two gears. See, e.g., U.S. Pat. Nos. 1,849,944; 2,252,209 and 4,507,948. Such a device, however, has several limitations relating to the small size of the convolutions that can be formed and the flexibility necessary to quickly adjust the machine from making cores having convolutions of one height to making cores having convolutions of a different height.
Another machine for making convoluted cores is a reciprocating press machine, such as a Robinson fin machine. See, e.g., U.S. Pat. Nos. 3,760,624 and 5,722,145. The Robinson fin machine uses two opposed dies, each moveable toward and away from the other in a vertical forming stroke to form the convolutions in a sheet of material that is fed between the dies. As with the rolling fin machines discussed above, however, the Robinson fin machine generally is used to make cores having relatively small convolutions, typically two inches or less. In addition, if a different core type or pattern is desired, a different machine set up is required. On-line set up operations include setting stripper heights, setting strokes, and setting tool height relative to the strippers. All of this is time consuming, non-productive, and obviously undesirable, especially when the manufacturer specializes in serving customers with special needs and low volume orders.
A type of pleat forming machine is known to make accordion bellows and lamp shades wherein the machine includes a laterally moveable pusher bar and a vertically moveable stripper bar parallel to it and normally spaced laterally from it above a table. Generally, the stripper bar reciprocates along a path extending perpendicular to the moving web of material while the pusher bar reciprocates along a path extending generally parallel to the moving web, toward and away from the reciprocating stripper bar. The pleats are formed by compressing respective sections of web material between the two bars during each reciprocation cycle of the bars. Specifically, when the pusher bar and stripper bar are moved together, a section of sheet material is disposed between the two bars and is folded into a pleat. After each pleat is formed the stripper bar is raised, permitting the just formed pleat to pass by. See, e.g., U.S. Pat. Nos. 2,677,993; 4,201,119 and 4,650,102 incorporated herein by reference. Such machines, however, are used to fold paper or cardboard for forming accordion bellows or pleated lamp shades or to fold filter media. They have not previously been known to be used or to be useful for folding more robust materials, such as metals, including aluminum.
In view of the above, it should be appreciated that there is still a need for a machine that forms a continuous sheet of thermally conductive material, such as aluminum, into a convoluted heat exchanger core and which readily makes cores having convolutions ranging in height from two inches or less up to and exceeding twelve inches. In addition, the machine should permit quick adjustments to the size of the convolutions without removing machinery from the production line. The present invention satisfies these and other needs and provides further related advantages.